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Research Corner: MassBrowser

| By: Adam Lynn

The below is a guest blog post from Amir Houmansadr, co-author of “MassBrowser: Unblocking the Web for the Masses, By the Masses.” The post is part of a new series from OTF, Research Corner, where we’ll be highlighting interesting research relevant to Internet freedom on topics such censorship, circumvention tool development, and security analyses, for example. Note that the research we feature here was not supported through OTF funding and does not constitute an endorsement of any of the technologies involved or the research findings found herein, but is recapped here in an effort to further connect such research efforts with the broader internet freedom community. If you'd like to see your own research featured here, send us an email at [email protected]

What is MassBrowser?

MassBrowser is a volunteer-run censorship circumvention system. In MassBrowser, normal Internet users with access to the uncensored Internet (which we call Buddies) proxy traffic for censored Internet users. MassBrowser, however, is different from existing volunteer-based circumvention systems in several ways.

First, MassBrowser is based on the "Separation of Properties" principle, which states that the key functionality of a circumvention system is "blocking resistance", and additional properties like privacy should be offered as optional features to the clients (as opposed to being integrated into such services as mandatory properties). Note that MassBrowser does not neglect client privacy; instead it allows each individual client to choose her desired balance between blocking resistance, quality of service, and privacy for various censored websites. Therefore, a MassBrowser client who is comfortable with everyone knowing that she just browsed https://cnn.com, can use a single-hop proxy to browse https://cnn.com with very small latencies. On the other hand, a client who is not comfortable sharing the fact that she just updated her blog on https://wordpress.com/ can use a Tor-supporting Buddy to update her blog (with much higher latencies of course!).

Second, MassBrowser aims at attracting a gigantic number of volunteer Buddies. We take two directions toward this goal. (1) We use several techniques to optimize and minimize the traffic load on proxies. (2) MassBrowser's Buddy software uses a user-friendly GUI that allows each volunteer to specify which content categories she is willing to proxy for censored clients, and sets a bandwidth cap. Therefore, you can decide to proxy traffic to only the News websites, search engines, Tor, Telegram, or any combination of those websites. In the event that the initially assigned buddy has not granted connections to all of the censored client’s desired destinations, the MassBrowser server matches her with a buddy that does accepts the desired websites.

For further technical details of MassBrowser check out our white paper: https://web.cs.umass.edu/publication/docs/2018/UM-CS-2018-005.pdf

Its Current State

MassBrowser is in the beta release mode with early-adopter clients from around the world testing it on a daily basis. MassBrowser's code is open-source and available at https://github.com/SPIN-UMass/MassBrowser. We have built desktop versions for Mac and Windows which are available on the project's webpage: https://massbrowser.cs.umass.edu/. Building mobile versions for the client is one of our top-priorities.

Disclaimer: Given that MassBrowser is in beta form, it’s important to understand its security limitations and the risk involved in using it. Working as designed, MassBrowser will afford you the same level of privacy as using public VPNs or public HTTPS proxies. Therefore, the volunteer who is proxying your traffic will know your IP address as well as the websites you are browsing. Additionally, during the installation process, MassBrowser will ask you to install a local certificate in your Firefox browser. This local certificate is required for MassBrowser to implement an essential optimization technique called CDNBrowsing. This certificate can be removed at any time by going to your Firefox settings.

How to Get Involved

Want to get involved? There are several ways to help MassBrowser.

- You can become a Buddy of MassBrowser and proxy traffic for clients. MassBrowser will not be successful as a scalable circumvention solution unless widely adopted by volunteers. We hope to make that possible by offering volunteers control over what they proxy.

- MassBrowser has been built and maintained by a small group of academics (currently 2-3 graduate students working on it). If you have technical skills, get involved and help us with the code. If you have money, fund our research so we hire more talented students and improve our backend server!

- Your feedback will be priceless! Try out the Buddy and Client software (by visiting our webpage) and let us know how we should improve it. Or simply tell us why you did not like it! You can reach us with your questions and feedback by emailing at [email protected]